1. Field of the Invention
The present invention relates to a multi-mode current-allocating device, and more particularly to a multi-mode current-allocating device serving to coordinate and allocate power supplied by multiple parallel-connected server power supplies.
2. Description of the Related Art
With reference to FIG. 12, a parallel power supply system has multiple power supply devices 1 connected with each other in parallel. Each power supply device 1 receives an input voltage Vin and supplies a rated output voltage Vo to a load. When any of the power supply devices fails, the rest of power supply devices can still normally supply power to the load. The advantage of the parallel power supply system resides in higher system reliability, high operation efficiency and easy replacement and repair of individual parts.
Each power supply device 1 has a pre-stage power supply circuit 101, a post-stage power supply circuit 102, a pre-stage control circuit corresponding to the pre-stage power supply circuit 101, and a post-stage control circuit corresponding to the post-stage power supply circuit 102. The pre-stage power supply circuit 101 converts an input voltage Vin into a bus bar voltage V1, and is composed of an AC (Alternating Current) to DC (Direct Current) converter with a power factor correction (PFC) function. The post-stage power supply circuit 102 converts the bus bar voltage V1 into an output voltage Vo, and is composed of a DC to DC converter.
To ensure proper coordination and operation among the power supply devices 1, the post-stage control circuit is responsible for current-sharing operation such that the power supply devices 1 supply an equivalent current. However, conventional power supply devices 1 are designed to merely perform a single control mode. For example, as far as active current sharing control is concerned, there are control modes, such as automatic master current-sharing control, average current-sharing control, and the like. Hardware of the foregoing control circuit can only be adapted to a corresponding control mode. Should a different control mode be desired, the foregoing control circuit must be re-designed again.
Moreover, while the load is turning into a light-loading state, if the original current-sharing control mode remains for the power supply devices 1 to supply an equivalent current, not only does each power supply device 1 have a low power supply efficiency, but also the entire power supply system has an deteriorating operation efficiency and the overall power loss tends to be high.